Carers Benefit is €213.00 pw from January = €11,076pa. She will need €2,215 in tax credits to cover that. If she has any tax credits over that they could be transfered to you.
There may, depending on your income, be a possibility to also transfer some of her unused standard rate cut-off point. It depends on what your income is and how the cut-off is presently allocated. If you are already earning over €45,400 then no cut-off can be transferred from her to you. If you are already earning over your cut-off but less than €45,400 then you could transfer some and thereby reduce tax on some of your earnings from 41% to 20%.